The present invention relates to aluminum components for a substrate processing chamber and their methods of manufacture.
In the processing of a substrate in a substrate processing chamber, as in the manufacture of integrated circuits and displays, the substrate is typically exposed to energized gases that are capable of, for example, etching or depositing material on the substrate. The energized gases can also be provided to clean surfaces of the chamber. However, the energized gases can often comprise corrosive halogen-containing gases and other energized species that can corrode components of the chamber, such as enclosure walls of the chamber. For example, chamber components made of aluminum can chemically react with energized halogen-containing gases to form AlCl3 or AlF3, thereby corroding the components. The corroded portions of the components can flake off and contaminate the substrate, which reduces the substrate yield. Thus, the corroded components must often be replaced or removed from the chamber and cleaned, resulting in undesirable chamber downtime.
The corrosion resistance of a chamber component can be improved by forming a coating of a corrosion resistant material over surfaces of the component that are susceptible to corrosion, such as surfaces that would otherwise be exposed to the energized gas. For example, a coating of aluminum oxide can be formed on surfaces of an aluminum component by anodizing the aluminum component in an electrolytic cell. However, anodized aluminum oxide coatings often contain surface features such as pores, cracks, indentures, and other penetrating features that limit the ability of the anodized aluminum coating to protect the underlying aluminum component. For example, surface features that extend through the protective coating can allow corrosive gases to penetrate the coating and erode the underlying component material thereby causing the coating to flake off of the component. This can cause the coating itself to contaminate the chamber and the substrate being processed therein.
The performance of the anodized aluminum oxide layer can be improved by coating the anodized layer with a protective material, such as a fusible polymer or an organic fluid, to protect the aluminum article from surface scars and dents. This process, however, requires additional process steps to cure, dry or seal the protective layer. Such additional steps also augment the cost and time to manufacture the article.
It is also desirable to reduce or prevent the diffusion of impurities that are present in the underlying aluminum structure to the exposed surface of the component. Aluminum alloys, for example, 6061 aluminum alloy often contains trace elements of impurities such as chromium, iron, or manganese; and sometimes even calcium, potassium or magnesium. When the raw surface of the aluminum component is exposed to the plasma environment in the process chamber, the low vacuum pressure in the chamber as well as the elevated temperatures of the plasma can cause migration of the impurities to the exposed surface of the aluminum component. The resultant higher surface concentration of impurity is undesirable and can result in contamination of the substrate.
Another way to protect a chamber component is to utilize a high purity aluminum-magnesium alloy to form the chamber component itself. The surface of the component is anodized and then exposed to a halogen-containing species. The halogens diffuse through the aluminum oxide layer to form a protective magnesium halide layer immediately beneath the aluminum oxide layer. The magnesium halide layer renders the article's surface corrosion-resistant and the aluminum oxide layer protects the underlying magnesium halide layer. While this approach provides good corrosion resistance, it can also be costly because the aluminum-magnesium alloy is difficult to fabricate.
Thus, there is a need for aluminum components that exhibit improved corrosion resistance to energized gases. There is also a need for aluminum components having an aluminum oxide coating that exhibits improved corrosion resistance and is less susceptible to the erosion and flaking off of aluminum particles. There is a further need for an aluminum component that has a low level of surface impurity concentration.